This invention relates to a variable damper assembly and more particularly, to a variable damper assembly for use with a vehicle steering system and which includes an electronically controlled variable orifice valve which allows the damping characteristics of the damper assembly to be selectively and controllably altered based upon the speed and steering wheel angle of the vehicle.
Damper assemblies are typically used within a vehicle steering assembly to reduce the forces that are transmitted to the steering wheel that may result from irregularities in the road surface. In this manner, damper assemblies improve impact feel and reduce steering xe2x80x9cshimmyxe2x80x9d and xe2x80x9cnibblexe2x80x9d.
Damper assemblies provide a damping force which varies based upon the velocity of the damper according to a certain function, relationship or curve. Conventional damper assemblies typically have a single force versus velocity function or curve which does not vary based upon vehicle speed or other parameters. As a result, conventional damper assemblies have either a relatively high force/velocity curve which provides high damping of impacts while compromising steering effort, or have a relatively low force/velocity curve which maintains power steering effort at a desirable level, but does not substantially reduce steering shimmy and nibble.
There is therefore a need for a variable damper assembly which provides maximum impact resistance and shimmy and nibble reduction at relatively high vehicle speeds and neutral steering positions, while providing sufficient power steering capabilities at relatively low speeds and during parking maneuvers.
A first advantage of the invention is that it provides a variable damper assembly for use with a vehicle steering system which overcomes some or all of the previously delineated drawbacks of prior damper systems and assemblies.
A second advantage of the invention is that it provides a variable damper assembly for use with a vehicle steering system which includes an electronically controlled variable orifice valve which provides for force-velocity relationships which are selectively variable based upon vehicle speed and steering wheel angle data.
A third advantage of the present invention is that it provides a variable damper assembly for a vehicle steering system which allows the damping characteristics of the damper assembly to be selectively and controllably altered based upon the speed and steering wheel angle of the vehicle.
A fourth advantage of the present invention is that it provides a variable damper assembly for a vehicle steering system which provides relatively high damping at high vehicle speeds and relatively high power steering effort at low vehicle speeds and during parking maneuvers.
According to a first aspect of the present invention, a variable damper assembly is provided and includes a cylinder which forms a chamber containing an amount of fluid; a piston which is slidably disposed within the chamber and which is effective to divide the chamber into a first side and a second side; and a variable orifice valve which is fluidly coupled to the first the and the second side of the chamber and which allows a certain amount of pressurized fluid to flow between the first and the second side of the chamber, the variable orifice valve having a variable volume fluid flow path which is effective to selectively increase and decrease the fluid flow rate between the first and second sides of the chamber, thereby selectively altering the damping characteristics of the damper assembly.
These and other objects, aspects, features, and advantages of the present invention will become apparent from a consideration of the following specification and the attached drawings.